The delayed return means that Cristoforetti has broken the record for the longest single stay by a woman in space.

Soyuz offers the only working transport for astronauts and cosmonauts to and from the space station. NASA shut down its ageing shuttle program in 2011 and is working with private firms to develop a new spacecraft for human transport.

NASA continues to fly cargo missions to the space station, which orbits an average of 400 kilometers above Earth.